Google-sheets – How to transform a form created in Google Sheets into an App or something that can be used by multiple people that also autoupdates

Still don't have a solution for how to directly get values of unchecked checkboxes, but I was at least able to write a function that compares the correct answer to the submission.

This splits the correct answer into an array then compares each item to the submission:

function checkAnswer(answer, key) {
var kArray = key.split(', ');
var nArray = [];
for (i=0; i<kArray.length; i++) {
    if (answer.indexOf(kArray[i]) == -1) {
        nArray.push(kArray[i]);
    }
}
return nArray.join(", ");
}

Then I could call it every time I needed to report the boxes left unchecked. For example, with the doors question:

if (doors != correctDoors) {
  var doorsMessage = "Unlocked: " + checkAnswer(doors, correctDoors);
  report.push(doorsMessage);
}

At the end, I'll compile the report with:

report.join("\n"); 

And voila! The best I could do...

Ultimately, I'm still looking for how to directly get the unchecked boxes if anyone has a solution.

Part of my answer would be: this is a known bug (newly received form submissions do not respect the format of the columns that they are landing in, as they did in the old version of sheets).

Depending on what you are doing with the data afterwards, another option would be to reproduce the form submissions on another sheet, with the correct format. For example, if column E contained zip codes that should be 5 digits long and include leading zeros (if required), then you could use:

=ArrayFormula(TEXT('Form Responses'!E:E,"00000"))

on another sheet.

You would need to bring over all your other columns as well, though. Without getting too complicated, this can be reasonably easily achieved in the new version of Sheets, and format the column(s) as desired, with (eg):

=QUERY('Form Responses'!A:G,"select * format E '00000'",1)